1. Field of the Invention
The present invention relates to an electronic device capable of performing an enumeration process with power supplied from a battery unit, for example.
2. Description of the Related Art
A USB device, that is an electronic device based on a Universal Serial Bus (USB) standard, is capable of receiving power from an external device via a USB cable. Japanese Patent Laid-Open Nos. 2007-20398 and 2007-68333 disclose a USB device capable of receiving power from an external device via a USB cable.
Performing an enumeration process between a USB device and an external device allows notification to the external device of what kind of device the USB device is. Japanese Patent Laid-Open No. 2007-20398 discloses a USB device which performs an enumeration process based on the USB standard with power received from an external device via a USB cable.
However, the amount of power supplied from an external device to a USB device disadvantageously depends on the capability of the external device. In this case, a lower capability of an external device may not provide power supply enough for performing an enumeration process, which may prevent start of the enumeration process.
The amount of power supplied from an external device to a USB device may vary in accordance with a load state of the external device. This may cause another problem that an enumeration process may possibly end in the middle for some load states of the external device.